England's FA said it is investigating allegations that referee David Coote had a discussion with a friend about issuing a yellow card to a player the day before a match, allegations which the under-fire referee has denied.
On Tuesday, The Sun newspaper said the friend had jokingly told Coote to issue a yellow card to then-Leeds United player Ezgjan Alioski during a second-tier match against West Bromwich Albion in 2019 so that he could place a bet with bookmakers.
Coote yellow carded Alioski in the match the following day, and later sent a message to the fan saying: "I hope you backed as discussed".
Coote said he had always refereed with integrity.
"I strongly refute these false and defamatory allegations," he said in a statement.
"Whatever issues I may have had in my personal life they have never affected my decision making on the field. I have always held the integrity of the game in the highest regard, refereeing matches impartially and to the best of my ability."
A spokesperson for the FA said: "These are very serious allegations and we are investigating as a -matter of urgency."
The PGMOL, English soccer's referees' body, said the facts needed to be established.
"We adopt a zero-tolerance approach to any breach of our Integrity Code of Conduct, which is signed by all match officials on an annual basis," the body added.
"PGMOL Board is committed to taking the appropriate action should any breach of that code be proven."
Leeds United did not immediately respond to an emailed request for comment.
Coote is already being investigated for separate incidents by the FA, PGMOL and European soccer governing body Uefa, who have also suspended him.
A video of the 42-year-old emerged this month which showed him allegedly abusing Liverpool and their former manager Jurgen Klopp.
"David Coote remains suspended and subject to an ongoing disciplinary process by PGMOL, separate to the investigation into this matter which will be carried out independently by The FA," the PGMOL added.
"We will be making no further comment at this stage."